Airbag ignition circuits, in particular for motor vehicles, are typically connected to a pyrotechnic firing pellet, which actuates a gas generator when current is supplied and thereby triggers an airbag. Electrically, such firing pellets correspond to an ohmic resistance. Beginning at the time of the airbag ignition, the firing pellet is supplied with a predetermined triggering current for a predetermined duration in order to trigger the airbag. Recently, however, it has become possible to connect electronic ignition circuits to an inductance or to magnetic actuators. Particularly popular is the connection of so-called LEA (low-energy actuator) magnetic actuators, that is, magnetic actuators that have a very low energy consumption. Such LEA magnetic actuators are usually used in active headrests or in electrical or electronic circuits used for activating roll bars. In airbag ignition circuits connected to such LEA magnetic actuators, there is no explosion of an firing pellet, but rather a magnetic field built up by an ignition current moves an actuator.
Most electronic airbag ignition circuits of the related art, which are used for supplying current to a magnetic actuator, have an output stage that includes a so-called high side and a so-called low side. Both the high side as well as the low side of such output stages is each essentially made up of a switching element, via which an inductance of a magnet actuator connected to the output stage of the airbag ignition circuit for the purpose of supplying current is connectable to the supply voltage terminals of an energy store. The switching element essentially forming the low side of the output stage is operated as a switch in order to discharge the ignition current, which flows through the inductance of the magnetic actuator when the airbag is triggered, to a supply voltage terminal, usually to ground.
If error conditions exist, if for example the airbag ignition circuit is short-circuited or if a short circuit occurs within the airbag ignition circuit, then in the related art the current flowing through an inductance connected to the airbag ignition circuit is limited by a circuit to a current value that lies below the ignition current required for igniting the airbag. Nevertheless, such short-circuit cases represent a substantial load for the low side, which may result in a destruction of the entire airbag ignition circuit and/or even in a failure to trigger the airbag in the event of accidents.